Synthetic diamond films and coatings may be grown from the vapor phase using chemical vapor deposition (CVD) such as oxy-acetylene flame combustion CVD, microwave plasma CVD, hot filament CVD etc. Hot filament CVD is one of the oldest and major method of depositing high quality CVD diamond on a large area (Ref: Growth of Diamond by sequential deposition and etching process using hot filament CVD, J. Wei and Y. Tzeng, Journal of Crystal Growth 128, (1993), 413-417). In one form, the deposition of a synthetic diamond film on a substrate using CVD requires an activated gas phase that is activated by high temperature and/or plasma excitation, with the gas phase including a carbon-containing species. Since the gas phase so described will tend to deposit both diamond and graphite on the substrate, the gas phase must also include a species such as atomic hydrogen that preferentially etches graphite. This CVD process also requires a substrate surface receptive to nucleation of diamond thereon and a temperature gradient between the gas phase and the substrate to drive the diamond producing species to the substrate. Other diamond films under the category of diamond-like carbon (DLC) consist of a mixture of sp2 and sp3 bonds with the higher quality DLC films having higher percentage of sp3 bonds. Many methods for depositing DLC have been demonstrated, including radio frequency plasma deposition, ion beam sputter deposition from a carbon target, ion beam sputtered carbon with ion beam assist, direct ion beam deposition, dual ion beam deposition, laser ablation deposition from a carbon target, and ion beam assisted evaporation of carbon [Ref: U.S. Pat. No. 5,635,245].
The use of diamond films produced by CVD processes in a decorative application and use of DLC coatings on gem media are further described in patent applications 2006/0182883 and 2003/0224167. Additionally the prior art includes various references to the application of DLC coatings to various media such as glass or polymeric materials with a view to improve the wear resistant characteristics or to assist in the preservation of sharp edges (Ref: U.S. Pat. Nos. 6,277,480, 5,795,648, 6,312,808, 5,635,245, 6,338,901, 6,335,086, 5,190,807 and 5,879,775). The growth of synthetic diamond films using high temperature CVD processes on various substrates is limited by the ability of the substrate to withstand high temperatures that are typically employed.
There are a multitude of non-diamond gemstones both natural and synthetic in origin, which are colored naturally or by means of a color enhancing treatment (Ref: Publication No. 20060182883), or clear, that can benefit from having a thin film diamond coating provided to the surface of the faceted and polished gemstones all around. There are various other substrates which serve a commercial application such as glass windows, a utility and or decorative application such as eyeglasses and/or eyeglass frames, metal decorative objects or substrates or jewelry objects, watch dials and/or watch glass and watch bands that would benefit from the application of a thin film of nano-crystalline diamond film. Many of the substrates mentioned here such as natural clear or colored non-diamond gemstones as well as color enhanced gemstones cannot be exposed to high temperatures for growth of synthetic diamond film using CVD techniques because these materials may crack or fracture and/or change color.
The physical characteristics that are generally accepted as being most important to gemstones are hardness, refractive index, color, thermal stability, chemical stability and toughness. Hardness defines the ability of a gemstone to resist scratching. Diamond is the hardest mineral with all other gemstone materials ranking in lower hardness such as sapphire at 9 on the Mohs scale down to precious as well as semi-precious gemstones such as emerald at 7.5, topaz at 8, apatite at 5 etc. Diamond, in addition its superior hardness, also possesses a very high refractive index which results in diamonds having a high brilliance.
Cubic Zirconia (CZ), the cubic crystalline form of Zirconium dioxide is a mineral that is widely synthesized for use as a diamond simulant. CZ has a high dispersive power as compared to diamond (0.06 vs. 0.044 of diamond) which results in increased prismatic fire in CZ that can be readily distinguished from diamond even by the untrained eye. CZ has a lower hardness at 8.5 vs. the 10 rating for diamond, as well as a lower refractive index than diamond. Due to CZs optical closeness to diamond including a high hardness, it has become a very popular low cost diamond simulant and is consumed in large quantities in the production of low cost jewelry.
In recent years manufacturers have sought ways to distinguish their product by supposedly “improving” CZ. Coating finished CZs with a film of DLC has been used where the resulting material is thought to provide an appearance that is more diamond-like overall by supposedly quenching the excess fire of CZ. The improvement in visual characteristics via DLC coating of CZ is subjective. The quality of DLC coatings and their ability to adhere to CZ is entirely dependent on the deposition process employed. DLC films appear colorless only in very thin layers which is another issue that has to be dealt with when coating on colorless CZ.
Yet another field in which gem media have been treated to improve their physical characteristics is in the area of fracture filling or clarity enhancement of such gem media. Examples include fracture filling of diamonds and emeralds. The filling materials that are used for diamonds are commonly of glass origin and, in the case of emeralds, the fillings may be of various types such as oils or polymers.
The filling of surface-reaching breaks in emeralds is a relatively common practice, for which various kinds of oils and a natural resin have historically been used. Now, however, epoxy resins are replacing the more traditional fillers such as cedar-wood oil and Canada balsam. The most widely known of these epoxy resins is sold under the brand name Opticon. The results of a broad study by GIA, of various fracture-filling materials found that Opticon treatment. (1) was, like the traditional materials, best detected using magnification with a variety of lighting techniques, and (2) although somewhat more durable than the traditional enhancements, was still altered in the course of routine jewelry cleaning and manufacturing processes. [Ref: Fracture Filling of Emeralds: Opticon and Traditional “Oils”, Gems And Gemmology, Volume 27, Number 2, Robert C. Kammerling, John I. Koivula, Robert E. Kane, Patricia Maddison, James E. Shigley, and Emmanuel Fritsch].
The first commercially available diamond fracture-filling treatment was developed in Israel in the mid 1980s. There are currently three main producers of the fracture filling treatment of diamonds and all three used proprietary formulations of a glass-like compound to fill-in the fractures that are opened to the surface by laser drilling operations. The refractive index of the filling compound is slightly less than diamond and the treatment can be easily distinguished by a color flash that can be observed in the filled regions when viewed at an angle. Also the fillings can be easily removed when the diamond is exposed to temperature above 150 C or if the diamond is exposed to acids which readily attack the glass-like filling.